Ann: Quarterly Activities Report, page-45

You can get significant differences in lining costs by the thickness of plastic you use...you can actually improve on lake pond recovery by using a very thin lining for a 10th of the cost compared with what would be required on land to prevent leakage / cuts etc. With ponds on the the lake it doesn't matter if you have some seepage from an enviro point of view. I suspect the EPA will want Kalium to use the highest grade plastic plus other measures which they may not have budgeted for in that $5.90 m2 figure.

Despite the speal from Kalium on lake ponds are better imo and you can line them pretty cheaply if you need to. It comes down to cost vs recovery.